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DR ANTHONY MELVIN CRASTO, Born in Mumbai in 1964 and graduated from Mumbai University, Completed his Ph.D from ICT, 1991,Matunga, Mumbai, India, in Organic Chemistry, The thesis topic was Synthesis of Novel Pyrethroid Analogues, Currently he is working with GLENMARK PHARMACEUTICALS LTD, Research Centre as Principal Scientist, Process Research (bulk actives) at Mahape, Navi Mumbai, India. Total Industry exp 30 plus yrs, Prior to joining Glenmark, he has worked with major multinationals like Hoechst Marion Roussel, now Sanofi, Searle India Ltd, now RPG lifesciences, etc. He has worked with notable scientists like Dr K Nagarajan, Dr Ralph Stapel, Prof S Seshadri, Dr T.V. Radhakrishnan and Dr B. K. Kulkarni, etc, He did custom synthesis for major multinationals in his career like BASF, Novartis, Sanofi, etc., He has worked in Discovery, Natural products, Bulk drugs, Generics, Intermediates, Fine chemicals, Neutraceuticals, GMP, Scaleups, etc, he is now helping millions, has 9 million plus hits on Google on all Organic chemistry websites. His friends call him Open superstar worlddrugtracker. His New Drug Approvals, Green Chemistry International, All about drugs, Eurekamoments, Organic spectroscopy international,
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The U.S. Food and Drug Administration issued a historic action today making the first gene therapy available in the United States, ushering in a new approach to the treatment of cancer and other serious and life-threatening diseases

The U.S. Food and Drug Administration issued a historic action today making the first gene therapy available in the United States, ushering in a new approach to the treatment of cancer and other serious and life-threatening diseases.

The FDA approved Kymriah (tisagenlecleucel) for certain pediatric and young adult patients with a form of acute lymphoblastic leukemia (ALL).

“We’re entering a new frontier in medical innovation with the ability to reprogram a patient’s own cells to attack a deadly cancer,” said FDA Commissioner Scott Gottlieb, M.D. “New technologies such as gene and cell therapies hold out the potential to transform medicine and create an inflection point in our ability to treat and even cure many intractable illnesses. At the FDA, we’re committed to helping expedite the development and review of groundbreaking treatments that have the potential to be life-saving.”

Kymriah, a cell-based gene therapy, is approved in the United States for the treatment of patients up to 25 years of age with B-cell precursor ALL that is refractory or in second or later relapse.

Kymriah is a genetically-modified autologous T-cell immunotherapy. Each dose of Kymriah is a customized treatment created using an individual patient’s own T-cells, a type of white blood cell known as a lymphocyte. The patient’s T-cells are collected and sent to a manufacturing center where they are genetically modified to include a new gene that contains a specific protein (a chimeric antigen receptor or CAR) that directs the T-cells to target and kill leukemia cells that have a specific antigen (CD19) on the surface. Once the cells are modified, they are infused back into the patient to kill the cancer cells.

ALL is a cancer of the bone marrow and blood, in which the body makes abnormal lymphocytes. The disease progresses quickly and is the most common childhood cancer in the U.S. The National Cancer Institute estimates that approximately 3,100 patients aged 20 and younger are diagnosed with ALL each year. ALL can be of either T- or B-cell origin, with B-cell the most common. Kymriah is approved for use in pediatric and young adult patients with B-cell ALL and is intended for patients whose cancer has not responded to or has returned after initial treatment, which occurs in an estimated 15-20 percent of patients.

“Kymriah is a first-of-its-kind treatment approach that fills an important unmet need for children and young adults with this serious disease,” said Peter Marks, M.D., Ph.D., director of the FDA’s Center for Biologics Evaluation and Research (CBER). “Not only does Kymriah provide these patients with a new treatment option where very limited options existed, but a treatment option that has shown promising remission and survival rates in clinical trials.”

The safety and efficacy of Kymriah were demonstrated in one multicenter clinical trial of 63 pediatric and young adult patients with relapsed or refractory B-cell precursor ALL. The overall remission rate within three months of treatment was 83 percent.

Treatment with Kymriah has the potential to cause severe side effects. It carries a boxed warning for cytokine release syndrome (CRS), which is a systemic response to the activation and proliferation of CAR T-cells causing high fever and flu-like symptoms, and for neurological events. Both CRS and neurological events can be life-threatening. Other severe side effects of Kymriah include serious infections, low blood pressure (hypotension), acute kidney injury, fever, and decreased oxygen (hypoxia). Most symptoms appear within one to 22 days following infusion of Kymriah. Since the CD19 antigen is also present on normal B-cells, and Kymriah will also destroy those normal B cells that produce antibodies, there may be an increased risk of infections for a prolonged period of time.

The FDA today also expanded the approval of Actemra (tocilizumab) to treat CAR T-cell-induced severe or life-threatening CRS in patients 2 years of age or older. In clinical trials in patients treated with CAR-T cells, 69 percent of patients had complete resolution of CRS within two weeks following one or two doses of Actemra.

Because of the risk of CRS and neurological events, Kymriah is being approved with a risk evaluation and mitigation strategy (REMS), which includes elements to assure safe use (ETASU). The FDA is requiring that hospitals and their associated clinics that dispense Kymriah be specially certified. As part of that certification, staff involved in the prescribing, dispensing, or administering of Kymriah are required to be trained to recognize and manage CRS and neurological events. Additionally, the certified health care settings are required to have protocols in place to ensure that Kymriah is only given to patients after verifying that tocilizumab is available for immediate administration. The REMS program specifies that patients be informed of the signs and symptoms of CRS and neurological toxicities following infusion – and of the importance of promptly returning to the treatment site if they develop fever or other adverse reactions after receiving treatment with Kymriah.

To further evaluate the long-term safety, Novartis is also required to conduct a post-marketing observational study involving patients treated with Kymriah.

The FDA granted Kymriah Priority Review and Breakthrough Therapy designations. The Kymriah application was reviewed using a coordinated, cross-agency approach. The clinical review was coordinated by the FDA’s Oncology Center of Excellence, while CBER conducted all other aspects of review and made the final product approval determination.

The FDA granted approval of Kymriah to Novartis Pharmaceuticals Corp. The FDA granted the expanded approval of Actemra to Genentech Inc.

The U.S. Food and Drug Administration today approved Vabomere for adults with complicated urinary tract infections (cUTI), including a type of kidney infection, pyelonephritis, caused by specific bacteria. Vabomere is a drug containing meropenem, an antibacterial, and vaborbactam, which inhibits certain types of resistance mechanisms used by bacteria.

The U.S. Food and Drug Administration today approved Vabomere for adults with complicated urinary tract infections (cUTI), including a type of kidney infection, pyelonephritis, caused by specific bacteria. Vabomere is a drug containing meropenem, an antibacterial, and vaborbactam, which inhibits certain types of resistance mechanisms used by bacteria.

“The FDA is committed to making new safe and effective antibacterial drugs available,” said Edward Cox, M.D., director of the Office of Antimicrobial Products in the FDA’s Center for Drug Evaluation and Research. “This approval provides an additional treatment option for patients with cUTI, a type of serious bacterial infection.”

The safety and efficacy of Vabomere were evaluated in a clinical trial with 545 adults with cUTI, including those with pyelonephritis. At the end of intravenous treatment with Vabomere, approximately 98 percent of patients treated with Vabomere compared with approximately 94 percent of patients treated with piperacillin/tazobactam, another antibacterial drug, had cure/improvement in symptoms and a negative urine culture test. Approximately seven days after completing treatment, approximately 77 percent of patients treated with Vabomere compared with approximately 73 percent of patients treated with piperacillin/tazobactam had resolved symptoms and a negative urine culture.

The most common adverse reactions in patients taking Vabomere were headache, infusion site reactions and diarrhea. Vabomere is associated with serious risks including allergic reactions and seizures. Vabomere should not be used in patients with a history of anaphylaxis, a type of severe allergic reaction to products in the class of drugs called beta-lactams.

To reduce the development of drug-resistant bacteria and maintain the effectiveness of antibacterial drugs, Vabomere should be used only to treat or prevent infections that are proven or strongly suspected to be caused by susceptible bacteria.

Vabomere was designated as a qualified infectious disease product (QIDP). This designation is given to antibacterial products that treat serious or life-threatening infections under the Generating Antibiotic Incentives Now (GAIN) title of the FDA Safety and Innovation Act. As part of its QIDP designation, Vabomere received a priority review.

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The U.S. Food and Drug Administration today granted accelerated approval to benznidazole for use in children ages 2 to 12 years old with Chagas disease. It is the first treatment approved in the United States for the treatment of Chagas disease.

The U.S. Food and Drug Administration today granted accelerated approval to benznidazole for use in children ages 2 to 12 years old with Chagas disease. It is the first treatment approved in the United States for the treatment of Chagas disease.

Chagas disease, or American trypanosomiasis, is a parasitic infection caused by Trypanosoma cruzi and can be transmitted through different routes, including contact with the feces of a certain insect, blood transfusions, or from a mother to her child during pregnancy. After years of infection, the disease can cause serious heart illness, and it also can affect swallowing and digestion. While Chagas disease primarily affects people living in rural parts of Latin America, recent estimates are that there may be approximately 300,000 persons in the United States with Chagas disease.

“The FDA is committed to making available safe and effective therapeutic options to treat tropical diseases,” said Edward Cox, M.D., director of the Office of Antimicrobial Products in the FDA’s Center for Drug Evaluation and Research.

The safety and efficacy of benznidazole were established in two placebo-controlled clinical trials in pediatric patients 6 to 12 years old. In the first trial, approximately 60 percent of children treated with benznidazole had an antibody test change from positive to negative compared with approximately 14 percent of children who received a placebo. Results in the second trial were similar: Approximately 55 percent of children treated with benznidazole had an antibody test change from positive to negative compared with 5 percent who received a placebo. An additional study of the safety and pharmacokinetics (how the body absorbs, distributes and clears the drug) of benznidazole in pediatric patients 2 to 12 years of age provided information for dosing recommendations down to 2 years of age.

Benznidazole was approved using the Accelerated Approval pathway. The Accelerated Approval pathway allows the FDA to approve drugs for serious conditions where there is unmet medical need and adequate and well-controlled trials establish that the drug has an effect on a surrogate endpoint that is reasonably likely to predict a clinical benefit to patients. Further study is required to verify and describe the anticipated clinical benefit of benznidazole.

The FDA granted benznidazole priority review and orphan product designation. These designations were granted because Chagas disease is a rare disease, and until now, there were no approved drugs for Chagas disease in the United States.

With this approval, benznidazole’s manufacturer, Chemo Research, S. L., is awarded a Tropical Disease Priority Review Voucher in accordance with a provision included in the Food and Drug Administration Amendments Act of 2007 that aims to encourage development of new drugs and biological products for the prevention and treatment of certain tropical diseases.

Benznidazole is an antiparasitic medication used in the treatment of Chagas disease.[2] While it is highly effective in early disease this decreases in those who have long term infection.[3] It is the first line treatment given its moderate side effects compared to nifurtimox.[1] It is taken by mouth.[2]

Medical uses

Benznidazole has a significant activity during the acute phase of Chagas disease, with a therapeutical success rate up to 80%. Its curative capabilities during the chronic phase are, however, limited. Some studies have found parasitologic cure (a complete elimination of T. cruzi from the body) in pediatric and young patients during the early stage of the chronic phase, but overall failure rate in chronically infected individuals is typically above 80%.[6]

However, some studies indicate treatment with benznidazole during the chronic phase, even if incapable of producing parasitologic cure, because it reduces electrocardiographic changes and a delays worsening of the clinical condition of the patient.[6]

Benznidazole has proven to be effective in the treatment of reactivated T. cruzi infections caused by immunosuppression, such as in people with AIDS or in those under immunosuppressive therapy related to organ transplants.[6]

Children

Benznidazole can be used in children and infants, with the same 5–7 mg/kg per day weight-based dosing regimen that is used to treat adult infections.[9] Children are found to be at a lower risk of adverse events compared to adults, possibly due to increased hepatic clearance of the drug. The most prevalent adverse effects in children were found to be gastrointestinal, dermatologic, and neurologic in nature. However, the incidence of severe dermatologic and neurologic adverse events is lower in the pediatric population compared to adults.[10]

Pregnant women

Studies in animals have shown that benznidazole can cross the placenta.[11] Due to its potential for teratogenicity, use of benznidazole in pregnancy is not recommended.[9]

Side effects

Side effects tend to be common and occur more frequently with increased age.[12] The most common adverse reactions associated with benznidazole are allergic dermatitis and peripheral neuropathy.[1] It is reported that up to 30% of people will experience dermatitis when starting treatment.[11][13] Benznidazole may cause photosensitization of the skin, resulting in rashes.[1] Rashes usually appear within the first 2 weeks of treatment and resolve over time.[13] In rare instances, skin hypersensitivity can result in exfoliative skin eruptions, edema, and fever.[13]Peripheral neuropathy may occur later on in the treatment course and is dose dependent.[1] It is not permanent, but takes time to resolve.[13]

Other adverse reactions include anorexia, weight loss, nausea, vomiting, insomnia, and dysguesia, and bone marrow suppression.[1] Gastrointestinal symptoms usually occur during the initial stages of treatment and resolves over time.[13] Bone marrow suppression has been linked to the cumulative dose exposure.[13]

Contraindications

Benznidazole should not be used in people with severe liver and/or kidney disease.[12] Pregnant women should not use benznidazole because it can cross the placenta and cause teratogenicity.[11]

Under anaerobic conditions, the nitro group of nitroimidazoles is believed to be reduced by the pyruvate:ferredoxin oxidoreductase complex to create a reactive nitro radical species.[14] The nitro radical can then either engage in other redox reactions directly or spontaneously give rise to a nitrite ion and imidazole radical instead.[15] The initial reduction takes place because nitroimidazoles are better electron acceptors for ferredoxin than the natural substrates.[14] In mammals, the principal mediators of electron transport are NAD+/NADH and NADP+/NADPH, which have a more positive reduction potential and so will not reduce nitroimidazoles to the radical form.[14] This limits the spectrum of activity of nitroimidazoles so that host cells and DNA are not also damaged. This mechanism has been well-established for 5-nitroimidazoles such as metronidazole, but it is unclear if the same mechanism can be expanded to 2-nitroimidazoles (including benznidazole).[15]

Biotie Therapies Holding , under license from Roche , is developing tozadenant (phase 3, as of August 2017) for the treatment of Parkinson’s disease.

SYN-115, a potent and selective adenosine A2A receptor antagonist, is in phase III clinical trials at Biotie Therapeutics for the treatment of Parkinson’s disease, as an adjunjunctive therapy with levodopa. Phase 0 trials were are underway at the National Institute on Drug Abuse (NIDA) for the treatment of cocaine dependency, but no recent development has been reported.

The A2A receptor modulates the production of dopamine, glutamine and serotonin in several brain regions. In preclinical studies, antagonism of the A2A receptor resulted in increases in dopamine levels, which gave rise to the reversal of motor deficits.

Originally developed at Roche, SYN-115 was acquired by Synosia in 2007, in addition to four other drug candidates with potential for the treatment of central nervous system (CNS) disorders. Under the terms of the agreement, Synosia was responsible for clinical development and in some cases commercialization, while Roche retained the right to opt-in to two preselected programs.

In 2010, the compound was licensed to UCB by Synosia Therapeutics for development and commercialization worldwide.

In February 2011, Synosia (previously Synosis Therapeutics) was acquired by Biotie Therapeutics, and in 2014, Biotie regained global rights from UCB.

Representative examples of A2AAdoR antagonists.

Tozadenant, also known as 4-hydroxy-N-(4-methoxy-7-(4-morpholinyl)benzo[d]thiazol-2-yl)-4-methylpiperidine-l-carboxamide or SYN115, is an adenosine A2A receptor antagonist. The A2A receptor modulates the production of

dopamine, glutamine and serotonin in several brain regions. In preclinical studies, antagonism of the A2A receptor resulted in increases in dopamine levels, which gave rise to the reversal of motor deficits.

Tozadenant is currently phase III clinical trials for the treatment of Parkinson’s disease as an adjunctive therapy with levodopa. It has also been explored for the treatment of cocaine dependency.

Adenosine modulates a wide range of physiological functions by interacting with specific cell surface receptors. The potential of adenosine receptors as drug targets was first reviewed in 1982. Adenosine is related both structurally and metabolically to the bioactive nucleotides adenosine triphosphate (ATP), adenosine diphosphate (ADP), adenosine monophosphate (AMP) and cyclic adenosine monophosphate (cAMP); to the biochemical methylating agent S-adenosyl-L-methione (SAM); and structurally to the coenzymes NAD, FAD and coenzyme A; and to RNA. Together adenosine and these related compounds are important in the regulation of many aspects of cellular metabolism and in the modulation of different central nervous system activities.

[0003]

The adenosine receptors have been classified as A1, A2A, A2B and A3receptors, belonging to the family of G protein-coupled receptors. Activation of aderosine receptors by adenosine initiates signal transduction mechanisms. These mechanisms are dependent on the receptor associated G protein. Each of the adenosine receptor subtypes has been classically characterized by the adenylate cyclase effector system, which utilises cAMP as a second messenger. The A1and A3 receptors, coupled with Gi proteins inhibit adenylate cyclase, leading to a decrease in cellular cAMP levels, while A2A and A2Breceptors couple to Gs proteins and activate adenylate cyclase, leading to an increase in cellular cAMP levels. It is known that the A1receptor system activates phospholipase C and modulates both potassium and calcium ion channels. The A3 subtype, in addition to its association with adenylate cyclase, also stimulates phospholipase C and activates calcium ion channels.

[0004]

The A1 receptor (326-328 amino acids) was cloned from various species (canine, human, rat, dog, chick, bovine, guinea-pig) with 90-95% sequence identify among the mammalian species. The A2Areceptor (409-412 amino acids) was cloned from canine, rat, human, guinea pig and mouse. The A2B receptor (332 amino acids) was cloned from human and mouse and shows 45% homology with the human A1 and A2A receptors. The A3 receptor (317-320 amino acids) was cloned from human, rat, dog, rabbit and sheep.

[0005]

The A1 and A2A receptor subtypes are proposed to play complementary roles in adenosine’s regulation of the energy supply. Adenosine, which is a metabolic product of ATP, diffuses from the cell and acts locally to activate adenosine receptors to decrease the oxygen demand (A1) or increase the oxygen supply (A2A) and so reinstate the balance of energy supply: demand within the tissue. The actions of both subtypes is to increase the amount of available oxygen to tissue and to protect cells against damage caused by a short term imbalance of oxygen. One of the important functions of endogenous adenosine is preventing damage during traumas such as hypoxia, ischemia, hypotension and seizure activity.

[0006]

Furthermore, it is known that the binding of the adenosine receptor agonist to mast cells expressing the rat A3 receptor resulted in increased inositol triphosphate and intracellular calcium concentrations, which potentiated antigen induced secretion of inflammatory mediators. Therefore, the A3 receptor plays a role in mediating asthmatic attacks and other allergic responses.

[0007]

Adenosine is a neurotransmitter able to modulate many aspects of physiological brain function. Endogenous adenosine, a central link between energy metabolism and neuronal activity, varies according to behavioral state and (patho)physiological conditions. Under conditions of increased demand and decreased availability of energy (such as hypoxia, hypoglycemia, and/or excessive neuronal activity), adenosine provides a powerful protective feedback mechanism. Interacting with adenosine receptors represents a promising target for therapeutic intervention in a number of neurological and psychiatric diseases such as epilepsy, sleep, movement disorders (Parkinson or Huntington’s disease), Alzheimer’s disease, depression, schizophrenia, or addiction. An increase in neurotransmitter release follows traumas such as hypoxia, ischemia and seizures. These neurotransmitters are ultimately responsible for neural degeneration and neural death, which causes brain damage or death of the individual. The adenosine A1agonists mimic the central inhibitory effects of adenosine and may therefore be useful as neuroprotective agents. Adenosine has been proposed as an endogenous anticonvulsant agent, inhibiting glutamate release from excitatory neurons and inhibiting neuronal firing. Adenosine agonists therefore may be used as antiepileptic agents. Furthermore, adenosine antagonists have proven to be effective as cognition enhancers. Selective A2A antagonists have therapeutic potential in the treatment of various forms of dementia, for example in Alzheimer’s disease, and of neurodegenerative disorders, e.g. stroke. Adenosine A2A receptor antagonists modulate the activity of striatal GABAergic neurons and regulate smooth and well-coordinated movements, thus offering a potential therapy for Parkinsonian symptoms. Adenosine is also implicated in a number of physiological processes involved in sedation, hypnosis, schizophrenia, anxiety, pain, respiration, depression, and drug addiction (amphetamine, cocaine, opioids, ethanol, nicotine, and cannabinoids). Drugs acting at adenosine receptors therefore have therapeutic potential as sedatives, muscle relaxants, antipsychotics, anxiolytics, analgesics, respiratory stimulants, antidepressants, and to treat drug abuse. They may also be used in the treatment of ADHD (attention deficit hyper-activity disorder).

[0008]

An important role for adenosine in the cardiovascular system is as a cardioprotective agent. Levels of endogenous adenosine increase in response to ischemia and hypoxia, and protect cardiac tissue during and after trauma (preconditioning). By acting at the A1 receptor, adenosine A1 agonists may protect against the injury caused by myocardial ischemia and reperfusion. The modulating influence of A2Areceptors on adrenergic function may have implications for a variety of disorders such as coronary artery disease and heart failure. A2Aantagonists may be of therapeutic benefit in situations in which an enhanced anti-adrenergic response is desirable, such as during acute myocardial ischemia. Selective antagonists at A2A Areceptors may also enhance the effectiveness of adenosine in terminating supraventricula arrhytmias.

[0009]

Adenosine modulates many aspects of renal function, including renin release, glomerular filtration rate and renal blood flow. Compounds which antagonize the renal affects of adenosine have potential as renal protective agents. Furthermore, adenosine A3 and/or A2Bantagonists may be useful in the treatment of asthma and other allergic responses or and in the treatment of diabetes mellitus and obesity.

[0010]

Numerous documents describe the current knowledge on adenosine receptors, for example the following publications:

To a solution of (4-methoxy-7-morpholin-4-yl-benzothiazol-2-yl)-carbamic acid phenyl ester (3.2 g, 8.3 mmol) and N-ethyl-diisopropyl-amine (4.4 ml, 25 mmol) in trichloromethane (50 ml) is added a solution of 4-hydroxy-4-methyl-piperidine in trichloromethane (3 ml) and tetrahydrofurane (3 ml) and the resulting mixture heated to reflux for 1 h. The reaction mixture is then cooled to ambient temperature and extracted with saturated aqueous sodium carbonate (15 ml) and water (2×5 ml). Final drying with magnesium sulphate and evaporation of the solvent and recrystallization from ethanol afforded the title compound as white crystals (78% yield), mp 236° C. MS: m/e=407(M+H+).

Novel deuterated forms of tozadenant are claimed. Also claimed are compositions comprising them and method of modulating the activity of adenosine A2A receptor (ADORA2A), useful for treating Parkinson’s diseases. Represents new area of patenting to be seen from CoNCERT Pharmaceuticals on tozadenant. ISR draws attention towards WO2016204939 , claiming controlled-release tozadenant formulations.

This invention relates to deuterated forms of morpholinobenzo[d]thiazol-2-yl)-4-methylpiperidine-1-carboxamide compounds, and pharmaceutically acceptable salts thereof. This invention also provides compositions comprising a compound of this invention and the use of such compositions in methods of treating diseases and conditions that are beneficially treated by administering an adenosine A2A receptor antagonist.

Many current medicines suffer from poor absorption, distribution, metabolism and/or excretion (ADME) properties that prevent their wider use or limit their use in certain indications. Poor ADME properties are also a major reason for the failure of drug candidates in clinical trials. While formulation technologies and prodrug strategies can be employed in some cases to improve certain ADME properties, these approaches often fail to address the underlying ADME problems that exist for many drugs and drug candidates. One such problem is rapid metabolism that causes a number of drugs, which otherwise would be highly effective in treating a disease, to be cleared too rapidly from the body. A possible solution to rapid drug clearance is frequent or high dosing to attain a sufficiently high plasma level of drug. This, however, introduces a number of potential treatment problems such as poor patient compliance with the dosing regimen, side effects that become more acute with higher doses, and increased cost of treatment. A rapidly metabolized drug may also expose patients to undesirable toxic or reactive metabolites.

[3] Another ADME limitation that affects many medicines is the formation of toxic or biologically reactive metabolites. As a result, some patients receiving the drug may experience toxicities, or the safe dosing of such drugs may be limited such that patients receive a suboptimal amount of the active agent. In certain cases, modifying dosing intervals or formulation approaches can help to reduce clinical adverse effects, but often the formation of such undesirable metabolites is intrinsic to the metabolism of the compound.

[4] In some select cases, a metabolic inhibitor will be co- administered with a drug that is cleared too rapidly. Such is the case with the protease inhibitor class of drugs that are used to treat HIV infection. The FDA recommends that these drugs be co-dosed with ritonavir, an inhibitor of cytochrome P450 enzyme 3A4 (CYP3A4), the enzyme typically responsible for their metabolism (see Kempf, D.J. et al., Antimicrobial agents and chemotherapy, 1997, 41(3): 654-60). Ritonavir, however, causes adverse effects and adds to the pill burden for HIV patients who must already take a combination of different drugs. Similarly, the

CYP2D6 inhibitor quinidine has been added to dextromethorphan for the purpose of reducing rapid CYP2D6 metabolism of dextromethorphan in a treatment of pseudobulbar affect.

Quinidine, however, has unwanted side effects that greatly limit its use in potential combination therapy (see Wang, L et al., Clinical Pharmacology and Therapeutics, 1994, 56(6 Pt 1): 659-67; and FDA label for quinidine at http://www.accessdata.fda.gov).

[5] In general, combining drugs with cytochrome P450 inhibitors is not a satisfactory strategy for decreasing drug clearance. The inhibition of a CYP enzyme’s activity can affect the metabolism and clearance of other drugs metabolized by that same enzyme. CYP inhibition can cause other drugs to accumulate in the body to toxic levels.

[6] A potentially attractive strategy for improving a drug’s metabolic properties is deuterium modification. In this approach, one attempts to slow the CYP-mediated metabolism of a drug or to reduce the formation of undesirable metabolites by replacing one or more hydrogen atoms with deuterium atoms. Deuterium is a safe, stable, non-radioactive isotope of hydrogen. Compared to hydrogen, deuterium forms stronger bonds with carbon. In select cases, the increased bond strength imparted by deuterium can positively impact the ADME properties of a drug, creating the potential for improved drug efficacy, safety, and/or tolerability. At the same time, because the size and shape of deuterium are essentially identical to those of hydrogen, replacement of hydrogen by deuterium would not be expected to affect the biochemical potency and selectivity of the drug as compared to the original chemical entity that contains only hydrogen.

[7] Over the past 35 years, the effects of deuterium substitution on the rate of metabolism have been reported for a very small percentage of approved drugs (see, e.g., Blake, MI et al, J Pharm Sci, 1975, 64:367-91; Foster, AB, Adv Drug Res 1985, 14: 1-40 (“Foster”); Kushner, DJ et al, Can J Physiol Pharmacol 1999, 79-88; Fisher, MB et al, Curr Opin Drug Discov Devel, 2006, 9: 101-09 (“Fisher”)). The results have been variable and unpredictable. For some compounds deuteration caused decreased metabolic clearance in vivo. For others, there was no change in metabolism. Still others demonstrated increased metabolic clearance. The variability in deuterium effects has also led experts to question or dismiss deuterium modification as a viable drug design strategy for inhibiting adverse metabolism (see Foster at p. 35 and Fisher at p. 101).

[8] The effects of deuterium modification on a drug’s metabolic properties are not predictable even when deuterium atoms are incorporated at known sites of metabolism. Only by actually preparing and testing a deuterated drug can one determine if and how the rate of metabolism will differ from that of its non-deuterated counterpart. See, for example, Fukuto et al. (J. Med. Chem. 1991, 34, 2871-76). Many drugs have multiple sites where metabolism is possible. The site(s) where deuterium substitution is required and the extent of deuteration necessary to see an effect on metabolism, if any, will be different for each drug.

LY2606368 is a small-molecule Chk-1 inhibitors invented by Array and being developed by Eli Lilly and Company. Lilly is responsible for all clinical development and commercialization activities. Chk-1 is a protein kinase that regulates the tumor cell’s response to DNA damage often caused by treatment with chemotherapy. In response to DNA damage, Chk-1 blocks cell cycle progression in order to allow for repair of damaged DNA, thereby limiting the efficacy of chemotherapeutic agents. Inhibiting Chk-1 in combination with chemotherapy can enhance tumor cell death by preventing these cells from recovering from DNA damage.

Prexasertib (LY2606368) is a small molecule checkpoint kinase inhibitor, mainly active against CHEK1, with minor activity against CHEK2. This causes induction of DNA double-strand breaks resulting in apoptosis. It is in development by Eli Lilly. [1]

an aminopyrazole compound, or a pharmaceutically acceptable salt thereof or a solvate of the salt, that inhibits Chkl and is useful for treating cancers characterized by defects in deoxyribonucleic acid (DNA) replication, chromosome segregation, or cell division.

Chkl is a protein kinase that lies downstream from Atm and/or Atr in the DNA damage checkpoint signal transduction pathway. In mammalian cells, Chkl is phosphorylated in response to agents that cause DNA damage including ionizing radiation (IR), ultraviolet (UV) light, and hydroxyurea. This phosphorylation which activates Chkl in mammalian cells is dependent on Atr. Chkl plays a role in the Atr dependent DNA damage checkpoint leading to arrest in S phase and at G2M. Chkl phosphorylates and inactivates Cdc25A, the dual-specificity phosphatase that normally dephosphorylates cyclin E/Cdk2, halting progression through S-phase. Chkl also phosphorylates and inactivates Cdc25C, the dual specificity phosphatase that dephosphorylates cyclin B/Cdc2 (also known as Cdkl) arresting cell cycle progression at the boundary of G2 and mitosis (Fernery et al, Science, 277: 1495-1, 1997). In both cases, regulation of Cdk activity induces a cell cycle arrest to prevent cells from entering mitosis in the presence of DNA damage or unreplicated DNA. Various inhibitors of Chkl have been reported. See for example, WO 05/066163,

WO 04/063198, WO 03/093297 and WO 02/070494. In addition, a series of aminopyrazole Chkl inhibitors is disclosed in WO 05/009435.

However, there is still a need for Chkl inhibitors that are potent inhibitors of the cell cycle checkpoints that can act effectively as potentiators of DNA damaging agents. The present invention provides a novel aminopyrazole compound, or a pharmaceutically acceptable salt thereof or solvate of the salt, that is a potent inhibitor of Chkl . The compound, or a pharmaceutically acceptable salt thereof or a solvate of the salt, potently abrogates a Chkl mediated cell cycle arrest induced by treatment with DNA damaging agents in tissue culture and in vivo. Furthermore, the compound, or a pharmaceutically acceptable salt thereof or a solvate of the salt, of the present invention also provides inhibition of Chk2, which may be beneficial for the treatment of cancer. Additionally, the lack of inhibition of certain other protein kinases, such as CDKl, may provide a -2- therapeutic benefit by minimizing undesired effects. Furthermore, the compound, or a pharmaceutically acceptable salt thereof or a solvate of the salt, of the present invention inhibits cell proliferation of cancer cells by a mechanism dependent on Chkl inhibition.

A solution of tert-butyl 3-(2-(3-(5-bromopyrazin-2-ylamino)-lH-pyrazol-5-yl)-3- methoxyphenoxy)propylcarbamate (0.378 g, 0.730 mmol) and zinc cyanide (0.10 g, 0.870 mmol) in DMF (10 mL) is degassed with a stream of nitrogen for one hour and then -25- heated to 80 0C. To the reaction is added Pd(Ph3P)4 (0.080 g, 0.070 mmol), and the mixture is heated overnight. The reaction is cooled to room temperature and concentrated under reduced pressure. The residue is purified by silica gel chromatography (CH2Cl2/Me0H) to give 0.251 g (73%) of the title compound.

A 5 L flange-neck round-bottom flask equipped with an air stirrer rod and paddle, thermometer, pressure-equalizing dropping funnel, and nitrogen bubbler is charged with 5-(5-(2-hydroxy-6-methoxy-phenyl)-lH-pyrazol-3-ylamino)-pyrazine-2-carbonitrile (47.0 g, 152 mmol) and anhydrous THF (1.2 L). The stirred suspension, under nitrogen, is cooled to 0 0C. A separate 2 L 3 -necked round-bottom flask equipped with a large -28- magnetic stirring bar, thermometer, and nitrogen bubbler is charged with triphenylphosphine (44.0 g; 168 mmol) and anhydrous THF (600 mL). The stirred solution, under nitrogen, is cooled to 0 0C and diisopropylazodicarboxylate (34.2 g; 169 mmol) is added and a milky solution is formed. After 3-4 min, a solution of7-butyl-N-(3- hydroxypropyl)-carbamate (30.3 g, 173 mmol) in anhydrous THF (100 mL) is added and the mixture is stirred for 3-4 min. This mixture is then added over 5 min to the stirred suspension of starting material at 0 0C. The reaction mixture quickly becomes a dark solution and is allowed to slowly warm up to room temperature. After 6.5 h, more reagents are prepared as above using PPh3 (8 g), DIAD (6.2 g) and carbamate (5.4 g) in anhydrous THF (150 mL). The mixture is added to the reaction mixture, cooled to -5 0C and left to warm up to room temperature overnight. The solvent is removed in vacuo. The resulting viscous solution is loaded onto a pad of silica and product is eluted with ethyl acetate. The concentrated fractions are separately triturated with methanol and resulting solids are collected by filtration. The combined solids are triturated again with methanol (400 mL) and then isolated by filtration and dried in vacuo at 50 0C overnight to give 31.3 g of desired product. LC-ES/MS m/z 466.2 [M+ 1]+.

5-(5-(2-Hydroxy-6-methoxyphenyl)-lH-pyrazol-3-ylamino)pyrazine-2- carbonitrile (618 g, 1.62 mol) is slurried in tetrahydrofuran (6.18 L, 10 volumes) and chilled to -5 to 0 0C with an acetone/ice bath. Triethylamine (330 g, 3.25 mol) is added through an addition funnel over 30 – 40 min at -5 to 5 0C. The resulting slurry is stirred at -5 to 5 0C for 60 – 90 min. The insoluble triethylamine hydrochloride is filtered and the solution of the phenol ((5-(2-hydroxy-6-methoxyphenyl)-lH-pyrazol-3- ylamino)pyrazine-2-carbonitrile) collected in an appropriate reaction vessel. The cake is rinsed with THF (1.24 L). The THF solution of the phenol is held at 15 to 20 0C until needed.

Triphenylphosphine (1074 g, 4.05 mol) is dissolved at room temperature in THF (4.33 L). The clear colorless solution is cooled with an acetone/ice bath to -5 to 5 0C. Diisopropylazodicarboxylate (795 g, 3.89 mol) is added dropwise through an addition funnel over 40 – 60 min, keeping the temperature below 10 0C. The resulting thick white slurry is cooled back to -5 to 0 0C. tert-Butyl 3-hydroxypropylcarbamate (717g, 4.05 moles) is dissolved in a minimum of THF (800 mL). The tert-butyl 3- hydroxypropylcarbamate/THF solution is added, through an addition funnel, over 20 – 30 -35- min at -5 to 5 0C to the reagent slurry. The prepared reagent is stirred in the ice bath at -5 to 0 0C until ready for use.

The prepared reagent slurry (20%) is added to the substrate solution at 15 to 20 0C. The remaining reagent is returned to the ice bath. The substrate solution is stirred at ambient for 30 min, then sampled for HPLC. A second approximately 20% portion of the reagent is added to the substrate, stirred at ambient and sampled as before. Addition of the reagent is continued with monitoring for reaction completion by HPLC. The completed reaction is concentrated and triturated with warm methanol (4.33 L, 50 – 60 0C) followed by cooling in an ice bath. The resulting yellow precipitate is filtered, rinsed with cold MeOH (2 L), and dried to constant weight to provide 544 g (72%) of the title compound, mp 214 – 216 0C; ES/MS m/z 466.2 [M+l]+.

tert-Butyl 3-(2-(3-(5-cyanopyrazin-2-ylamino)-lH-pyrazol-5-yl)-3- methoxyphenoxy)propylcarbamate (1430 g, 3.07 mol) is slurried with acetone (21.5 L) in a 30 L reactor. Methanesulfonic acid (1484 g, 15.36 mol) is added through an addition funnel in a moderate stream. The slurry is warmed to reflux at about 52 0C for 1 to 3 h and monitored for reaction completion by HPLC analysis. The completed reaction is cooled from reflux to 15 to 20 0C over 4.5 h. The yellow slurry of 2-pyrazinecarbonitrile, 5-[[5-[-[2-(3-aminopropyl)-6-methoxyphenyl]-lH-pyrazol-3-yl]amino] dimesylate salt is filtered, rinsed with acetone (7 L) and dried in a vacuum oven. The dimesylate salt, (1608 g, 2.88 mol) is slurried in water (16 L). Sodium hydroxide (aqueous 50%, 228 g, 2.85 mol) is slowly poured into the slurry. The slurry is -36- heated to 60 0C and stirred for one hour. It is then cooled to 16 0C over 4 h and filtered. The wet filter cake is rinsed with acetone (4 L) and dried to constant weight in a vacuum oven at 40 0C to provide 833 g (94%) of 2-pyrazinecarbonitrile, 5-[[5-[-[2-(3- aminopropyl)-6-methoxyphenyl]-lH-pyrazol-3-yl]amino] monomesylate monohydrate. mp 222.6 0C; ES/MS m/z 366.2 [M+l]+.

Crude 2-pyrazinecarbonitrile, 5 -[ [5 – [- [2-(3 -aminopropyl)-6-methoxyphenyl]- IH- pyrazol-3-yl] amino] monomesylate monohydrate is purified using the following procedure. The technical grade 2-pyrazinecarbonitrile, 5-[[5-[-[2-(3-aminopropyl)-6- methoxyphenyl]-lH-pyrazol-3-yl] amino] mono mesylate mono hydrate (1221 g, 2.55 mol) is slurried in a solvent mixture of 1: 1 acetone/water (14.7 L). The solid is dissolved by warming the mixture to 50 – 55 0C. The solution is polish filtrated while at 50 – 55 0C through a 0.22μ cartridge filter. The solution is slowly cooled to the seeding temperature of about 42 – 45 0C and seeded. Slow cooling is continued over the next 30 – 60 min to confirm nucleation. The thin slurry is cooled from 38 to 15 0C over 3 h. A vacuum distillation is set up and the acetone removed at 110 – 90 mm and 20 – 30 0C. The mixture is cooled from 30 to 15 0C over 14 h, held at 15 0C for 2 h, and then filtered. The recrystallized material is rinsed with 19: 1 water/acetone (2 L) and then water (6 L) and dried to constant weight in a vacuum oven at 40 0C to provide 1024 g (83.9%) of the title compound, mp 222.6 0C; ES/MS m/z 366.2 [M+l]+. X-ray powder diffraction (XRPD) patterns may be obtained on a Bruker D8

Advance powder diffractometer, equipped with a CuKa source (λ=l.54056 angstrom) operating at 40 kV and 40 mA with a position-sensitive detector. Each sample is scanned between 4° and 35° in °2Θ ± 0.02 using a step size of 0.026° in 2Θ ± 0.02 and a step time of 0.3 seconds, with a 0.6 mm divergence slit and a 10.39 mm detector slit. Primary and secondary Soller slits are each at 2°; antiscattering slit is 6.17 mm; the air scatter sink is in place. -37-

Characteristic peak positions and relative intensities:

Differential scanning calorimetry (DSC) analyses may be carried out on a Mettler- Toledo DSC unit (Model DSC822e). Samples are heated in closed aluminum pans with pinhole from 25 to 350 0C at 10 °C/min with a nitrogen purge of 50 mL/min. Thermogravimetric analysis (TGA) may be carried out on a Mettler Toledo TGA unit (Model TGA/SDTA 85Ie). Samples are heated in sealed aluminum pans with a pinhole from 25 to 350 0C at 10 0C /min with a nitrogen purge of 50 mL/min.

The thermal profile from DSC shows a weak, broad endotherm form 80 – 1400C followed by a sharp melting endotherm at 222 0C, onset (225 0C, peak). A mass loss of 4% is seen by the TGA from 25 – 140 0C.

X-Ray Powder Diffraction, Crystalline Example 1 Obtain the XRPD patterns of the crystalline solids on a Bruker D4 Endeavor X-ray powder diffractometer, equipped with a CuKa source (λ = 1.54060 A) and a Vantec detector, operating at 35 kV and 50 mA. Scan the sample between 4 and 40° in 2Θ, with a step size of 0.0087° in 2Θ and a scan rate of 0.5 seconds/step, and with 0.6 mm divergence, 5.28mm fixed anti-scatter, and 9.5 mm detector slits. Pack the dry powder on a quartz sample holder and obtain a smooth surface using a glass slide. It is well known in the crystallography art that, for any given crystal form, the relative intensities of the diffraction peaks may vary due to preferred orientation resulting from factors such as crystal morphology and habit. Where the effects of preferred orientation are present, peak intensities are altered, but the characteristic peak positions of the polymorph are unchanged. See, e.g. The U. S. Pharmacopeia 35 – National Formulary 30 Chapter <941> Characterization of crystalline and partially crystalline solids by XRPD Official December 1, 2012-May 1, 2013. Furthermore, it is also well known in the

crystallography art that for any given crystal form the angular peak positions may vary slightly. For example, peak positions can shift due to a variation in the temperature or humidity at which a sample is analyzed, sample displacement, or the presence or absence of an internal standard. In the present case, a peak position variability of ± 0.2 in 2Θ will take into account these potential variations without hindering the unequivocal identification of the indicated crystal form Confirmation of a crystal form may be made based on any unique combination of distinguishing peaks (in units of ° 2Θ), typically the more prominent peaks. The crystal form diffraction patterns, collected at ambient temperature and relative humidity, were adjusted based on NIST 675 standard peaks at 8.85 and 26.77 degrees 2-theta,

Characterize a prepared sample of crystalline 5-(5-(2-(3-aminopropoxy)-6-methoxyphenyl)- lH-pyrazol-3-ylamino)pyrazine-2-carbonitrile (S)-lactate monohydrate by an XPRD pattern using CuKa radiation as having diffraction peaks (2-theta values) as described in Table 1 below. Specifically the pattern contains a peak at 12.6 in

combination with one or more of the peaks selected from the group consisting of 24.8, 25.5, 8.1, 6.6, 12.3, and 16.3 with a tolerance for the diffraction angles of 0.2 degrees.

Combine a THF solution (22%) of i<?ri-butyl (3-(2-(2-cyanoacetyl)-3-methoxyphenoxy)propyl)carbamate (1.0 eqv, this is define as one volume) with hydrazine (35%, 1.5 eqv), acetic acid (glacial, 1.0 eqv), water (1 volume based on the THF solution) and methanol (2 volumes based on the THF solution). As this is a continuous operation, grams or kg is irrelevant in this processing methodology. Heat the resulting mixture to 130 °C and 1379 kPa with a rate of V/Q = 70 minutes (where V refers to the volume of the reactor and Q refers to flow rate), tau = 60. Extract the solution with toluene (4 volumes), water (1 volume), and sodium carbonate (10% aqueous, 1 eqv). Isolate the toluene layer and add to DMSO (0.5 volumes). Collect a solution of the intermediate compound i<?ri-butyl (3-(2-(3-amino- lH-pyrazol-5-yl)-3-methoxyphenoxy)

propyl)carbamate (26.59 kg, 91%) in 10 days, mp = 247.17 °C as a DMSO solution (3 volumes of product). N-ethylmorpholine (1.2 eqv) and 5-chloropyrazine-2-carbonitrile (1.15 eqv) in 2 volumes of DMSO is combined in a tube reactor at 80 °C, V/Q = 3 and tau = 170 minutes at ambient pressure. Add the product stream to methanol (20 vol). As a continuous process, filter the mixture and wash with methanol followed by MTBE. Air dry the material on the filter to give i<?ri-butyl (3-(2-(3-((5-cyanopyrazin-2-yl)amino)-lH-pyrazol-5-yl)-3-methoxyphenoxy) propyl)carbamate in a continuous fashion (22.2 kg, 88.7%, 8 days). Dissolve a solution of i<?ri-butyl (3-(2-(3-((5-cyanopyrazin-2-yl)amino)-lH-pyrazol-5-yl)-3-methoxyphenoxy) propyl)carbamate in formic acid (99%, 142 kg) at ambient temperature and agitate for 4 hours to provide an intermediate of 5-((5-(2-(3-aminopropoxy)-6-methoxyphenyl)-lH-pyrazol-3-yl)amino)pyrazine-2-carbonitrile formate. Dilute the solution with water (55 kg), (S)-lactic acid (30%, 176 kg) and distill the resulting mixture until < 22 kg formic acid remains. Crystallize the resulting residue from THF and wash with a THF -water (0.5% in THF) solution. Dry the wet cake at 30 °C at >10% relative humidity to give the title product as a white to yellow solid (24.04 kg, 85-90%), m.p. 157 °C.

A multidisciplinary team from Eli Lilly reports the development and implementation of eight continuous unit operations for the synthesis of ca. 3 kg API per day under CGMP conditions (K. P. Cole et al., Science2017, 356, 1144). The recent drive toward more potent APIs that have a low annual demand (<100 kg) has made continuous synthesis a viable alternative to traditional batch processes with advantages which include reducing equipment footprint and worker exposure. In this report the authors describe the enablement of three continuous synthetic steps followed by a salt formation, using surge tanks between steps to allow each step to be taken offline if online PAT detects a loss in reaction performance. A combination of MSMPRs (mixed-suspension, mixed-product removal) vessels, plug-flow reactors, and dissolve-off filters were used to perform the chemistry, with an automated 20 L rotary evaporator used to concentrate process streams and perform solvents swaps. This paper gives an excellent account of the potential solutions to continuous API synthesis and is well worth a read for anyone contemplating such methodology.

Continuous crystallisation, shown here, and subsequent filtration have been the most difficult-to-develop part of the prexasertib production process

Eli Lilly has taken an important step away from traditional batch process drug manufacturing by using an industry-first continuous process to make a compound for phase I and II clinical trials. Workers at Lilly’s Kinsale site in Ireland, did three steps involved in producing cancer drug candidate prexasertib continuously, under current good manufacturing practice (CGMP) standards that ensure safety for human consumption.

Continuous processing relies on chemical and physical changes happening as substances flow through pipes. Isolated steps of this type are already well-established in the pharmaceutical industry. However, Lilly ‎principal research scientist Kevin Cole stresses that a series including reaction and purification steps like this has not been demonstrated before. And the company wants to go much further.

The complex synthesis of prexasertib even requires the use of toxic hydrazine – used as a rocket fuel. As a result, and because of prexasertib’s toxicity, the drug was a good candidate to test out a comprehensive flow chemistry setup

In batch processes different chemical reaction and purification steps are typically done in large, costly vessels. However, this can be uneconomical when small amounts of drug molecules are needed for early stage clinical trials and, because drugs are getting more potent, increasingly in mainstream production.

By contrast, small volume continuous flow processing runs in more compact equipment in fume hoods. Flow systems can adapt to different processes, with cheap parts that can either be dedicated to specific drugs or readily replaced. The US Food and Drug Administration (FDA) has also been promoting continuous manufacturing because it integrates well with advanced process analytical technology. This helps pharmaceutical companies make high quality drugs with less FDA oversight.

Lilly chose prexasertib as its test case for such a process because it’s challenging to make. It is a chain of three aromatic rings, and one challenge comes because its central ring is formed using hydrazine. Hydrazine is used as a component in rocket fuel, and is also highly toxic. A second challenge comes from prexasertib itself, which, as a potent kinase inhibitor, is toxic to healthy cells, as well as cancerous ones, even at low doses. Lilly therefore wants to minimise its workers’ exposure.

Feeding the plant

Cole and his colleagues at Lilly’s labs in Indianapolis, US, have developed flow processes for three of the seven steps involved in prexasertib production. They start with the hydrazine step, which they could safely speed up by super-heating in the continuous process. After aqueous workup purification the solution of the two-ring intermediate solution runs into a ‘surge tank’. From there the solution flows intermittently into a rotary evaporator that removes solvents to concentrate it.

The second continuous flow step adds the third of prexasertib’s rings. In this case, the Lilly team purified the intermediate by crystallising it and filtering it out, washing away impurities. They could then redissolve the pure intermediate in formic acid, which also removes a protecting group, giving the desired prexasertib molecule. Automating this was probably the hardest part, Cole says. ‘Development of a predictive filtration model, equipment design and identification of formic acid as the solvent were keys to success,’ he explains. The final flow step then starts converting prexasertib to its final lactate salt form.

After developing the processes and systems in Indianapolis, Lilly shipped them to be equipped in an existing facility at its Kinsale manufacturing site at the cost of €1 million (£870,000). Once the prexasertib system was installed, the company was able to make 3kg of raw material per day for clinical trials. Cole describes the level of manual intervention needed as ‘moderate’.

Klavs Jensen from the Massachusetts Institute of Technology calls the paper describing the work ‘terrific’. ‘This work marks an important milestone in the continuous manufacturing of pharmaceuticals by demonstrating the feasibility of producing a modern kinase inhibitor under CGMP conditions,’ he says.

Likewise, Brahim Benyahia from Loughborough University, UK, calls this achievement ‘very interesting’. ‘The paper is another example that demonstrates the benefits and feasibility of the integrated continuous approach in pharma,’ he says.

Cole adds that Lilly has several other similar projects in advanced stages of development intended for the €35 million small-volume continuous plant it recently built in Kinsale. ‘We are committed to continuous manufacturing as well as full utilisation of our new facility,’ he says.

Correction: This article was updated on 16 June 2017 to clarify the chronology of the completion of the Kinsale, Ireland plant

On March 3, 2014, the U.S. FDA granted Fast Track designation to the development of rapastinel as an adjunctive therapy in treatment-resistant major depressive disorder.[3] As of 2015, the drug had completed phase II clinical development for this indication.[4] On January 29, 2016, Allergan (who acquired Naurex in July 2015) announced that rapastinel had received Breakthrough Therapydesignation from the U.S. FDA for adjunctive treatment of major depressive disorder.

Rapastinel belongs to a group of compounds, referred to as glyxins (hence the original developmental code name of rapastinel, GLYX-13),[5] that were derived via structural modification of B6B21, a monoclonal antibody that similarly binds to and modulates the NMDA receptor.[2][6][7] The glyxins were invented by Joseph Moskal, the co-founder of Naurex.[5] Glyxins and B6B21 do not bind to the glycine site of the NMDA receptor but rather to a different regulatory site on the NMDA receptor complex that serves to allosterically modulate the glycine site.[8] As such, rapastinel is technically an allosteric modulator of the glycine site of the NMDA receptor, and hence is more accurately described as a functional glycine site weak partial agonist.[8]

Highlights

Standard peptide coupling strategy in the solution-phase is utilized for synthesis.

Abstract

Rapastinel (GLYX-13) is a C-amidated tetrapeptide drug under clinical development for adjunctive treatment of major depressive disorder (MDD). Rapastinel features two consecutive proline residues centered at the peptide sequence (Thr-Pro-Pro-Thr-NH2), which are detrimental to its biological activity. In this communication, we report the synthesis of very close structural analogues of rapastinel comprising silaproline (Sip) as proline surrogate. By virtue of its enhanced lipophilicity and metabolic stability, Sip introduction in the native rapastinel sequence is expected to improve its pharmacokinetic profiles.

Graphical abstract

Depression is the most common neuropsychiatric diseases, seriously affecting people’s health.In China With accelerated pace of life, increasing the incidence of depression was significantly higher social pressure.

[0003] Drug therapy is the primary means of treatment of depression.The main treatment drugs, including tricyclic antidepressants such as imipramine, amitriptyline and the like; selective serotonin reuptake inhibitors such as fluoxetine, sertraline and the like; serotonin / norepinephrine dual uptake inhibitors such as venlafaxine, duloxetine.However, commonly used drugs slow onset, usually takes several weeks to months, and there is not efficient and toxicity obvious shortcomings.

[0004] GLYX-13 is a new antidepressant, Phase II clinical study is currently underway.It does this by regulating the brain NMDA (N_ methyl -D- aspartate) receptors play a role, and none of them have serious side effects such as ketamine and R-rated, such as hallucinations and schizophrenia and so on.GLYX-13 can play a strong, fast and sustained antidepressant effects, the onset time of less than 24 hours, and the sustainable average of 7 days.As a peptide drug, GLYX-13 was well tolerated and safe to use.

[0005] GLYX-13 is a tetrapeptide having the sequence structure Thr-Pro-Pro-Thr, which is a free N-terminal amino group, C terminal amide structure.GLYX-13 synthesis methods include traditional methods of two solid-phase peptide synthesis and liquid phase peptide synthesis, because of its short sequence, the amount of solid phase synthesis of amino acids, high cost, and difficult to achieve a lot of preparation.A small amount of liquid phase amino acids, high yield can be prepared in large quantities.

The present invention can be further described by the following examples.

An N-methyl-D-aspartate (NMDA) receptor is a postsynaptic, ionotropic receptor that is responsive to, inter alia, the excitatory amino acids glutamate and glycine and the synthetic compound NMDA. The NMDA receptor (NMDAR) appears to controls the flow of both divalent and monovalent ions into the postsynaptic neural cell through a receptor associated channel and has drawn particular interest since it appears to be involved in a broad spectrum of CNS disorders. The NMDAR has been implicated, for example, in neurodegenerative disorders including stroke-related brain cell death, convulsive disorders, and learning and memory.

NMDAR also plays a central role in modulating normal synaptic transmission, synaptic plasticity, and excitotoxicity in the central nervous system. The NMDAR is further involved in Long-Term Potentiation (LTP), which is the persistent strengthening of neuronal connections that underlie learning and memory The NMDAR has been associated with other disorders ranging from hypoglycemia and cardiac arrest to epilepsy. In addition, there are preliminary reports indicating involvement of NMDA receptors in the chronic neurodegeneration of Huntington’s, Parkinson’s, and Alzheimer’s diseases. Activation of the NMDA receptor has been shown to be responsible for post-stroke convulsions, and, in certain models of epilepsy, activation of the NMDA receptor has been shown to be necessary for the generation of seizures. In addition, certain properties of NMDA receptors suggest that they may be involved in the information-processing in the brain that underlies consciousness itself. Further, NMDA receptors have also been implicated in certain types of spatial learning.

[0003] In view of the association of NMDAR with various disorders and diseases, NMDA-modulating small molecule agonist and antagonist compounds have been developed for therapeutic use. NMDA receptor compounds may exert dual (agonist/antagonist) effect on the NMDA receptor through the allosteric sites. These compounds are typically termed “partial agonists”. In the presence of the principal site ligand, a partial agonist will displace some of the ligand and thus decrease Ca flow through the receptor. In the absence of the principal site ligand or in the presence of a lowered level of the principal site ligand, the partial agonist acts to increase Ca++ flow through the receptor channel.

Example 2: Synthesis of GLYX-13

[00119] GLYX-13 was prepared as follows, using intermediates KSM-1 and KSM-2 produced in Example 1. The synthetic route for the same is provided in Figure 2.

[00120] In this stage, KSM -1 was reacted with 10%Pd/C in presence of methanol to produce a compound represented by Formula XI. The reaction was optimized and performed up to 4.0 kg scale in the production plant and observed consistent quality (>80% by HPLC%PA) and yields (80% to 85%).

[00121] The reaction scheme involved in this method is as follows:

[00122] Raw materials used for this method are illustrated in Table 7 as follows:

Table 7.

[00123] In stage A, 10% Palladium on Carbon (w/w, 50% wet) was charged into the pressure reactor at ambient temperature under nitrogen atmosphere. KSM-1 was dissolved in methanol in another container and sucked into above reactor under vacuum. Hydrogen pressure was maintained at 45-60 psi at ambient temperature for over a period of 5-6 hrs. Progress of the reaction mixture was monitored by HPLC for KSM-1 content; limit is not more than 5%.

Hyflow bed was prepared with methanol (Lot-II). The reaction mass was filtered through nutsche filter under nitrogen atmosphere and bed was washed with Methanol Lot-Ill. Filtrate was transferred into the reactor and distilled completely under reduced pressure at below 50 °C (Bath temperature) to get the syrup and syrup material was unloaded into clean and dry container and samples were sent to QC for analysis.

[00124] From the above reaction(s), 1.31 kg of compound represented by Formula XI was obtained with a yield of 89.31% and with a purity of 93.63%).

[00125] In this stage the compound represented by Formula XI obtained above was reacted with KSM-2 to produce a compound represented by Formula XII. This reaction was optimized and scaled up to 3.0 kg scale in the production plant and obtained 25% to 28% yields with UPLC purity (>95%).

[00126] The reaction scheme is as follows:

[00127] Raw materials used for this method are illustrated in Table 8 as follows:

Table 8.

[00128] Stage B: ethanol was charged into the reactor at 20 to 35 °C. Compound represented by Formula XI was charged into the reactor under stirring at 20 to 35 °C and reaction mass was cooled to -5 to 0°C. EDC.HC1 was charged into the reaction mass at -5 to 0 °C and reaction mass, was maintained at -5 to 0 °C for 10-15 minutes. N-Methyl morpholine was added drop wise to the above reaction mass at -5 to 0 °C and reaction mass was maintained at -5 to 0 °C for 10-15 minutes.

[00129] KSM-2 was charged into the reactor under stirring at -5 to 0 °C and reaction mass was maintained at -5 to 0 °C for 3.00 to 4.00 hours. The temperature of the reaction mass was raised to 20 to 35 °C and was maintained at 20 to 35 °C for 12 – 15 hours under stirring. (Note:

Monitor the reaction mass by HPLC for Stage A content after 12.0 hours and thereafter every 2.0 hours. The content of stage A should not be more than 2.0%). Ethanol was distilled out completely under vacuum at below 50 °C (Hot water temperature) and reaction mass was cooled to 20 to 35 °C. Water Lot-1 was charged into the residue obtained followed by 10% DCM-Isopropyl alcohol (Mixture of Dichloromethane Lot-1 & Isopropyl alcohol Lot-1 prepared in a cleaned HDPE container) into the reaction mass at 20 – 35 °C.

[00130] Both the layers were separated and the aqueous layer was charged into the reactor. 10%) DCM-Isopropyl alcohol (Mixture of Dichloromethane Lot-2 & Isopropyl alcohol Lot-2 prepared in a cleaned HDPE container) was charged into the reaction mass at 20 to 35 °C. Both the layers were separated and the aqueous layer was charged back into the reactor. 10%> IDCM-isopropyl alcohol (Mixture of Dichloromethane Lot-3 & Isopropyl alcohol Lot-3 prepared in a cleaned HDPE container) was charged into the reaction mass at 20 to 35 °C. Both the layers were separated and the aqueous layer was charged back into the reactor. 10%> DCM-Isopropyl alcohol (Mixture of Dichloromethane Lot-4 & Isopropyl alcohol Lot-4 prepared in a cleaned HDPE container) was charged into the reaction mass at 20 to 35 °C and separated both the layers. The above organic layers were combined and potassium hydrogen sulfate solution (Prepare a solution in a HDPE container by dissolving Potassium hydrogen sulfate Lot-1 in water Lot-2) was charged into the reaction mass at 20 to 35 °C. Separated both the layers and charged back organic layer into the reactor. Potassium hydrogen sulfate solution (Prepared a solution in a HDPE container by dissolving Potassium hydrogen sulfate Lot-2 in water Lot-3) was charged into the reaction mass at 20 to 35 °C. Separated both the layers and the organic layer was dried over Sodium sulfate and distilled out the solvent completely under vacuum at below 45 °C (Hot water temperature).

[00131] The above crude was absorbed with silica gel (100-200mesh) Lot-1 in

dichloromethane. Prepared the column with silica gel (100-200 mesh) Lot-2, and washed the silica gel bed with from Dichloromethane Lot-5 and charged the adsorbed compound into the column. Eluted the column with 0-10% Methanol Lot-1 in Dichloromethane Lot-5 and analyzed fractions by HPLC. Solvent was distilled out completely under vacuum at below 45 °C (Hot water temperature). Methyl tert-butyl ether Lot-1 was charged and stirred for 30 min. The solid was filtered through the Nutsche filter and washed with Methyl tert-butyl ether Lot-2 and

samples were sent to QC for complete analysis. (Note: If product quality was found to be less than 95%, column purification should be repeated).

[00132] From the above reaction(s), 0.575 kg of compound represented by Formula XII was obtained with a yield of 17% and with a purity of 96.28%).

[00133] In this reaction step the compound of Formula XII obtained above was reacted with 10%oPd in presence of methanol to produce GLYX-13. This reaction was optimized and performed up to 2.8 kg scale in the production plant and got 40% to 45% of yields with UPLC purity >98%.

[00134] The reaction scheme involved in this method is as follows:

i

[00135] Raw materials used for this method are illustrated in Table 9 as follows:

Table 9.

30 Nitrogen cylinder – – – – – 31 Hydrogen cylinder – – – – –

[00136] In an exemplary embodiment of stage C, 10% Palladium Carbon (50% wet) was charged into the pressure reactor at ambient temperature under nitrogen atmosphere. Compound of Formula XII was dissolved in methanol in a separate container and sucked into the reactor under vacuum. Hydrogen pressure was maintained 45-60 psi at ambient temperature over a period of 6-8 hrs. Progress of the reaction was monitored by HPLC for stage-B (compound represented by Formula XII) content (limit is not more than 2%). If HPLC does not comply continue the stirring until it complies. Prepared the hyflow bed with methanol (Lot-II) and the reaction mass was filtered through hyflow bed under nitrogen atmosphere, and the filtrate was collected into a clean HDPE container. The bed was washed with Methanol Lot-Ill and the filtrate was transferred into the Rota Flask and distilled out the solvent completely under reduced pressure at below 50°C (Bath temperature) to get the crude product. The material was unloaded into clean HDPE container under Nitrogen atmosphere.

[00137] Neutral Alumina Lot-1 was charged into the above HDPE container till uniform mixture was formed. The neutral Alumina bed was prepared with neutral alumina Lot-2 and dichloromethane Lot-1 in a glass column. The neutral Alumina Lot-3 was charged and

Dichloromethane Lot-2 into the above prepared neutral Alumina bed. The adsorbed compound was charged into the column from op.no.11. The column was eluted with Dichloromethane Lot-2 and collect 10 L fractions. The column was eluted with Dichloromethane Lot-3 and collected 10 L fractions. The column was eluted with Dichloromethane Lot-4 and Methanol Lot-4 (1%) and collected 10 L fractions. The column was eluted with Dichloromethane Lot-5 and Methanol Lot-5 (2%) and collected 10 L fractions. The column was eluted with Dichloromethane Lot-6 and Methanol Lot-6 (3%) and collected 10 L fractions. The column was eluted with

[00138] Ensured the reactor is clean and dry. The pure fractions were transferred into the reactor.

[00139] The solvent was distilled off completely under vacuum at below 45 °C (Hot water temperature). The material was cooled to 20 to 35°C. Charged Dichloromethane Lot- 10 and Methanol Lot- 10 into the material and stirred till dissolution. Activated carbon was charged into the above mixture at 20 to 35°C and temperature was raised to 45 to 50 °C.

[00140] Prepared the Hyflow bed with Hyflow Lot-2 and Methanol Lot-11 Filtered the reaction mass through the Hy-flow bed under nitrogen atmosphere and collect the filtrate into a clean FIDPE container. Prepared solvent mixture with Dichloromethane Lot-11 and Methanol Lot- 12 in a clean FIDPE container and washed Nutsche filter with same solvent. Charged filtrate in to Rota evaporator and distilled out solvent under vacuum at below 50°C. Dry the compound in Rota evaporator for 5 to 6 hours at 50°C, send sample to QC for Methanol content (residual solvent) which should not be more than 3000 ppm. The material was cooled to 20 to 35 °C and the solid material was unloaded into clean and dry glass bottle. Samples were sent to QC for complete analysis.

[00141] From the above reaction(s), 0.92 kg of Glyx-13 was obtained with a yield of 43.5% and with a purity of 99.73%.

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ICH Q11 Q and A Document

The topic of starting materials has been a vexed topic for some period. Indeed concerns relating to lack of clarity and issues pertaining to practical implementation led the EMA in Sept 2014 to publish a reflection paper—Reflection on the requirements for selection and justification of starting materials for the manufacture of chemical active substances.(10) The paper sought to outline key issues as well as authority expectations; specific areas of interest identified included the following:

1.

Variance in interpretation between applicant and reviewer.

2.

The registration of short syntheses that employ complex custom-made starting materials.

3.

Lack of details preventing authorities being able to assess the suitability of a proposed registered starting material and its associated control strategy.

While the consensus was that overall this provided a useful perspective of at least the EMA’s interpretation of ICH Q11(2) and requirements for starting…

The U.S. Food and Drug Administration today approved Mavyret (glecaprevir and pibrentasvir) to treat adults with chronic hepatitis C virus (HCV) genotypes 1-6 without cirrhosis (liver disease) or with mild cirrhosis, including patients with moderate to severe kidney disease and those who are on dialysis. Mavyret is also approved for adult patients with HCV genotype 1 infection who have been previously treated with a regimen either containing an NS5A inhibitor or an NS3/4A protease inhibitor but not both.

The U.S. Food and Drug Administration today approved Mavyret (glecaprevir and pibrentasvir) to treat adults with chronic hepatitis C virus (HCV) genotypes 1-6 without cirrhosis (liver disease) or with mild cirrhosis, including patients with moderate to severe kidney disease and those who are on dialysis. Mavyret is also approved for adult patients with HCV genotype 1 infection who have been previously treated with a regimen either containing an NS5A inhibitor or an NS3/4A protease inhibitor but not both.

Mavyret is the first treatment of eight weeks duration approved for all HCV genotypes 1-6 in adult patients without cirrhosis who have not been previously treated. Standard treatment length was previously 12 weeks or more.

“This approval provides a shorter treatment duration for many patients, and also a treatment option for certain patients with genotype 1 infection, the most common HCV genotype in the United States, who were not successfully treated with other direct-acting antiviral treatments in the past,” said Edward Cox, M.D., director of the Office of Antimicrobial Products in the FDA’s Center for Drug Evaluation and Research.

Hepatitis C is a viral disease that causes inflammation of the liver that can lead to diminished liver function or liver failure. According to the Centers for Disease Control and Prevention, an estimated 2.7 to 3.9 million people in the United States have chronic HCV. Some patients who suffer from chronic HCV infection over many years may have jaundice (yellowish eyes or skin) and complications, such as bleeding, fluid accumulation in the abdomen, infections, liver cancer and death.

There are at least six distinct HCV genotypes, or strains, which are genetically distinct groups of the virus. Knowing the strain of the virus can help inform treatment recommendations. Approximately 75 percent of Americans with HCV have genotype 1; 20-25 percent have genotypes 2 or 3; and a small number of patients are infected with genotypes 4, 5 or 6.

The safety and efficacy of Mavyret were evaluated during clinical trials enrolling approximately 2,300 adults with genotype 1, 2, 3, 4, 5 or 6 HCV infection without cirrhosis or with mild cirrhosis. Results of the trials demonstrated that 92-100 percent of patients who received Mavyret for eight, 12 or 16 weeks duration had no virus detected in the blood 12 weeks after finishing treatment, suggesting that patients’ infection had been cured.

The most common adverse reactions in patients taking Mavyret were headache, fatigue and nausea.

Mavyret is not recommended in patients with moderate cirrhosis and contraindicated in patients with severe cirrhosis. It is also contraindicated in patients taking the drugs atazanavir and rifampin.

Hepatitis B virus (HBV) reactivation has been reported in HCV/HBV coinfected adult patients who were undergoing or had completed treatment with HCV direct-acting antivirals, and who were not receiving HBV antiviral therapy. HBV reactivation in patients treated with direct-acting antiviral medicines can result in serious liver problems or death in some patients. Health care professionals should screen all patients for evidence of current or prior HBV infection before starting treatment with Mavyret.

Glecaprevir (INN,[1] codenamed ABT-493) is a hepatitis C virus (HCV) nonstructural (NS) protein 3/4A protease inhibitor that was identified jointly by AbbVie and Enanta Pharmaceuticals. It is being developed as a treatment of chronic hepatitis C infection in co-formulation with an HCV NS5A inhibitor pibrentasvir. Together they demonstrated potent antiviral activity against major HCV genotypes and high barriers to resistance in vitro.[2]

Solithromycin exhibits excellent in vitro activity against a broad spectrum of Gram-positiverespiratory tractpathogens,[3][4] including macrolide-resistant strains.[5] Solithromycin has activity against most common respiratory Gram-(+) and fastidious Gram-(-) pathogens,[6][7] and is being evaluated for its utility in treating gonorrhea.

July 2016: Cempra Announces FDA Acceptance of IV and oral formulations of Solithera (solithromycin) New Drug Applications for in the Treatment of Community-Acquired Bacterial Pneumonia.[13]

Structure

X-ray crystallography studies have shown solithromycin, the first fluoroketolide in clinical development, has a third region of interactions with the bacterial ribosome,[14] as compared with two binding sites for other ketolides.

Macrolide antibiotics, such like erythromycin, azithromycin, and clarithromycin, have proven to be safe and effective for use in treating human infectious diseases such as community-acquired bacterial pneumonia (CABP), urethritis, and other infections.

Because of the importance of macrolide antibiotics, there has been growing recent interest in this area as exemplified by the new fourth-generation macrolide solithromycin , which is developed by Cempra Pharmaceuticals as the first fluoroketolide antibiotic that has recently completed phase III clinical trials and demonstrates potent activity against the pathogens associated with CABP, including macrolide- and penicillin-resistant isolates of S. pneumoniaeis

To date, all macrolide antibiotics are produced by chemical modification (semisynthesis) of erythromycin, a natural product produced on the ton scale by fermentation. Depicted are erythromycin and the approved semisynthetic macrolide antibiotics clarithromycin, azithromycin and telithromycin along with the dates of their FDA approval and the number of steps for their synthesis from erythromycin. The previous ketolide clinical candidate cethromycin and the current clinical candidate solithromycin are also depicted. It is evident that increasingly lengthy sequences are being employed in macrolide discovery efforts.

Potential causes for the formation of synthetic impurities that are present in solithromycin (1) during laboratory development are studied in the article. These impurities were monitored by HPLC, and their structures are identified on the basis of MS and NMR spectroscopy. In addition to the synthesis and characterization of these seven impurities, strategies for minimizing them to the level accepted by the International Conference on Harmonization (ICH) are also described.

PAPER

Identification, Characterization, Synthesis, and Strategy for Minimization of Potential Impurities Observed in the Synthesis of Solithromycin

Macrolide antibacterial agents are characterized by a large lactone ring to which one or more deoxy sugars, usually cladinose and desosamine, are attached. The first generation macrolide, erythromycin, was soon followed by second generation macrolides clarithromycin and azithromycin. Due to widespread of bacterial resistance semi-synthetic derivatives, ketolides, were developed. These, third generation macrolides, to which, for example, belongs telithromycin, are used to treat respiratory tract infections. Currently, a fourth generation macrolide, solithromycin (also known as CEM-101 ) belonging to the fluoroketolide class is in the pre-registration stage. Solithromycin is more potent than third generation macrolides, is active against macrolide-resistant strains, is well-tolerated and exerts good PK and tissue distribution.

One route of synthesis of solithromycin is disclosed in WO2004/080391 A2. Said route is based on the synthetic strategy disclosed in Tetrahedron Letters, 2005, 46, 1483-1487. It is formally a 10 step linear synthesis starting from clarithromycin. Its characteristics are a late cleavage of cladinose, a hexose deoxy sugar which is in ketolides replaced with a keto group, and a 3-step building up of the side chain. Most intermediates are amorphous or cannot be purified by crystallization, hence chromatographic separations are required.

WO 2009/055557 A1 describes a process, in which the linker part of the side chain (azidobutyl) is synthesized separately thus making the synthesis more convergent. In addition, the benzoyl protection group instead of the acetyl is used to protect the 3-hydroxy group of the tetrahydropyran moiety. The linker part of the side chain is introduced using 4-azidobutanamine which is prepared through a selective Staudinger monoreduction of 1 ,4-diazidobutane.

WO 2014/145210 A1 discloses several routes of synthesis all based on the use of already fully constructed side chain building blocks, or its protected forms, which are reacted with an imidazoyl carbamate still containing the protected cladinose moiety. After the introduction of the side chain, the cladinose is cleaved and the aniline group protected for the oxidation of the hydroxy group and the fluorination. After fluorination and deprotection or unmasking of the aniline group, solithromycin is obtained.

Synthesis of crude solithromycin

A third aspect of the invention is a process for providing crude solithromycin (the compound of formula 5) through a convergent synthesis that combines both aforementioned building blocks, the macrolide building block (compound of formula 3) and the side chain building block 3-(1 -(4-aminobutyl)-1 H-1 ,2,3-triazol-4-yl)aniline prepared as discussed above.

As shown in Scheme 4, first, the compound of formula 3 and 3-(1-(4-aminobutyl)-1 H-1 ,2,3-triazol-4-yl)aniline are reacted in the presence of a strong base, for example, DBU, in a suitable solvent, for example, MeCN, to give the compound of formula 4. In the last step, the acetyl protecting group of the hydroxy group located on position β to the dimethylamino substituent is cleaved in methanol.

As discussed above, the fluorination is performed in the presence of acetyl group in the pyran part of the molecule and prior to the incorporation of the side chain, which allows that both exchanging the protection group in the pyran part of the molecule and masking or protecting the aniline moiety from oxidation caused under fluorinating conditions can be avoided.

Scheme 4: Representation of the specific embodiment of the present invention.

In another aspect of the present invention a process is provided for purification of crude solithromycin.

Purification of crude solithromycin

Due to its properties, solithromycin is very difficult to purify. The amorphous material obtained after various syntheses is truly a challenge for further processing.

Chromatographic separation is very difficult and of poor resolution. Due to the basic polar functional groups, the compound and its related impurities all tend to “trail” on typical normal stationary phases that are considered suitable for industrial use, such as silica and alumina. Purification by crystallization is just as difficult unless the material is already sufficiently pure. Impurities inhibit its crystallization to such an extent that solutions in alcohols can be stable even in concentrations of several-fold above the saturation levels of the pure material. Such solutions refuse to crystallize even after weeks of stirring or cooling. Seeding with crystalline solithromycin has no effect and the added seeds simply dissolve. In addition, only limited purification is achieved in most solvents. Lower primary alcohols, particularly ethanol, are most efficient for purification by crystallization when this is possible, but give low recovery and the crystallization is most sensitive toward impurities, thus still demanding prior chromatographic separation.

Clearly an alternative method of purification would be advantageous. For this reason we developed a process for purification employing an acidic salt formation, for example solithromycin oxalate salt, freebasing back to solithromycin, and crystallization from ethanol (Scheme 5).

Scheme 5: Representation of a particular embodiment of the present invention.

The formation of crystalline salts from crude solithromycin may be inhibited by impurities and is dependent on the solvent used. Only a limited number of acids gave useful precipitates from solutions of crude solithromycin. Of these, the precipitation of the oxalate salt from isopropyl acetate (‘PrOAc) or 2-methyltetrahydrofuran (MeTHF) was found to be most efficient in regard to yields, reaction times and purification ability. Precipitation of the citrate salt from MeTHF also significantly increased purity. However, impurities strongly inhibited crystal growth rates, the reaction thus required longer times compared to the oxalate salt formation. Crystallization of salts from solutions of impure solithromycin was also found possible with D-(-)-tartaric, dibenzoyl-d-tartaric, 2,4-dihydroxybenzoic, 3,5-dihydroxybenzoic, and (R)-(+)-2-pyrrolidinone-5-carboxylic acids using ethyl acetate, isopropyl acetate or MeTHF as solvents, or their mixtures with methyl f-butyl ether, but the efficiency and purification abilities were inferior to both the oxalate and the citrate salt.

Some acids, such as (R)-(-)-mandelic, L-(+)-tartaric, p-toluenesulfonic, benzoic, malonic, 4-hydroxybenzoic, (-)-malic, and (+)-camphor-10-sulfonic acid formed insoluble amorphous precipitates without improving purity. Many other acids were found unable of forming any precipitate from impure solithromycin under the conditions tested.

A solution of (2S,3R,4S,6R)-4-(dimethylamino)-2-(((3R,5R,6R,7R,9R,13S,14R,Z)-14-ethyl-13-hydroxy-7-methoxy-3,5,7,9,11,13-hexamethyl-2,4,10-trioxooxacyclotetradec-11-en-6-yl)oxy)-6-methyltetrahydro-2H-pyran-3-yl acetate, 1 (313 g) in dichloromethane (2.22 L) was cooled to -25 °C. DBU (115 mL) followed by CDI (125 g) were added and temperature of the reaction was raised to 0°C. The completion of the reaction was followed by HPLC. Upon the completion, the pH of the reaction mixture was adjusted to 6 using 10% aqueous acetic acid. Layers were separated and organic layer was washed twice with water, dried over sodium sulphate and concentrated to afford compound 2 as white foam (HPLC purity: 90 area%).

A solution of (2R,3S,7R,9R,10R,11 R,13R,Z)-10-(((2S,3R,4S,6R)-3-acetoxy-4-(dimethylamino)-6-methyltetrahydro-2H-pyran-2-yl)oxy)-2-ethyl-9-methoxy-3,5,7,9,11,13-hexamethyl-6,12,14-trioxooxacyclotetradec-4-en-3-yl 1H-imidazole-1-carboxylate, 2 in THF (9 L) was cooled to 0 °C. DBU (115 mL) followed by NFSI (211 g) were added and reaction mixture was stirred at 0°C

A solution of (2S,3R,4S,6R)-4-(dimethylamino)-2-(((3R,5R,6R,7R,9R,13S,14R,Z)-14-ethyl-13-hydroxy-7-methoxy-3,5,7,9,1 1 , 13-hexamethyl-2,4, 10-trioxooxacyclotetradec-1 1-en-6-yl)oxy)-6-methyltetrahydro-2H-pyran-3-yl acetate, 1 (2.45 g) in THF (17 mL) was cooled to 0 °C. DBU (0.9 mL) followed by CDI (0.97 g) were added. The completion of the reaction was followed by HPLC. Upon the completion, reaction was diluted by addition of THF (34 mL). Temperature of the reaction was lowered to -10 °C. DBU (0.72 mL) was added followed by solution of NFSI (1.51 g) in THF (14 mL). Upon completion of the reaction, mixture was diluted with the addition of water/ZPrOAc (1 :4) mixture and layers were separated. Organic phase was washed with water (3 x 25 mL), dried over Na2S04, filtered and concentrated to afford compound 3 as a white foam (3.1 g, HPLC purity: 70 area%).

To isopropyl acetate (5.77 L) crude solithromycin (192 g, 72 area%) was added, afterwards the mixture was stirred at reflux and filtered to remove any insoluble material. The filtrate was then stirred at 55 °C and oxalic acid (14.91 g, 164 mmol) was added in one batch. The suspension was cooled to 20 °C in the course of 1 h, stirred for additional 1 h and the product was isolated by filtration, washed with isopropyl acetate (0.5 L), and dried at 40 °C under reduced pressure to give the oxalate salt (106 g): 87.81 area% by HPLC (UV at 228 nm). The evaporation of the filtrate gave a resinous material containing solithromycin that can be recovered by reprocessing (88 g, 61.13 area%).

The above oxalate salt (106 g) was dissolved in water (2.40 L) and washed with MeTHF (2 χ 1.00 L) and ethyl acetate (0.50 L). Aqueous ammonia (25%; 37 mL) was then added to the filtrate while stirring at 25 °C. The precipitated product was extracted with ethyl acetate two times (3.00 L and 0.50 L). The combined extracts were washed with water (0.50 L), dried over Na2S04 and evaporated under reduced pressure. To the residue ethanol (2 χ 0.4 L) was added and again evaporated to affect the solvent exchange. The residue was then dissolved in ethanol (300 mL). After stirring for 24 h at 25 °C, the crystallized product was isolated by filtration and drying at 40 °C under reduced pressure to give solithromycin as an off-white crystalline solid (42 g): 98.61 area% by HPLC (UV at 228 nm).

The filtrate was evaporated under reduced pressure to give a yellowish foam (29 g: 68.65 area% by HPLC (UV at 228 nm) that was used for reprocessing.